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Here is a basic diagram of the power feed to your house, according to what the power company said they found: R1 represents the additional series resistance due to the cable being corroded. R2 re...
Answer
#6: Post edited
by
Olin Lathrop
·
2020-08-04T13:29:51Z (over 3 years ago)
- Here is a basic diagram of the power feed to your house, according to what the power company said they found:
- 
- R1 represents the additional series resistance due to the cable being corroded. R2 represents the leakage current to ground due to the broken insulation. Both these can vary over time, whether it recently rained, and even recent usage. Significant usage will heat up R1, and various chemical effects can make R2 not even look like a resistor.
- However, this is still the basic concept. This alone explains nicely why the L2-G voltage is low, but not why L2-L1 could be lower than L2-G. For that we have to consider what is connected in the house.
- Here is the circuit considering some of what is in the house:
- 
- R3 shows the small but inevitable leakage and "phantom loads", and C1 capacitance between the wires and inside 240 V appliances.
- Note that both R3 and C1 can allow substantially more current than might be apparent at first glance. Modern appliances often use a little standby power, even when "off". There may be a clock, for example. Most modern appliances aren't turned on by actually switching main power directly by a button you touch. That would require way too large and expensive user buttons. Something has to always be on to sense when you press one of those little membrane panel buttons, for example.
- C1 isn't just the stray capacitance between wires in the walls. The large appliances in particular probably have hefty line filters to reduce their conducted emissions to just below the legal limit. There could easily be some deliberate capacitance across the power input for that purpose alone.
- The symptoms you found can be explained by the right relative values of the various components in the above circuit. To prove this, consider the extreme case where R1 and R2 are completely open:
- 
- With an infinite impedance voltmeter, you'd measure 120 V L1-G, 120 V L2-G, and 0 V L2-L1. Your actual case is somewhere between the top circuit and this last one. Hopefully you can see that with the various ratios between, R1, R2, R3, and C1, you can construct lots of different scenarios, including the one you actually had.
- <blockquote><ul>
- <li>The L1/G voltage difference was 120V (good).
- <li>The G/L2 voltage difference was 90V (bad).
- <li>The L1/L2 voltage difference was 30V (very bad!).
- </ul>
- </blockquote>
- Note that your numbers add up nicely if you assume the L2 connection from the street is completely open. In other words, all the L2 voltage you see is coming from L1. The 30 V L1-L2 is because phantom loads and leakage to ground on L2 pull down on what is getting dumped onto L2 from L1. That leakage is causing a 30 V drop, hence L2 is at 120 V - 30 V = 90 V. When you measure L2 to L1, you get that 30 V drop directly.
- In the context of the second schematic:<ul>
- <li>R1 = ∞
- <li>R2 = 3 * R3
- <li>C1 = 0
- </ul>
- This is all quite plausible, and doesn't require phase shifts to explain.
<h2>Summary</h2>- This simple scenario would exactly cause your measurements:
- 
I show R2 outside the house because it was originally drawn to model the leakage of the exposed cable to the ground. However, R2 is really the combination of all loads to ground on L2. The most substantial part of R2 may actually be in the house, in the form of phantom loads of 120 V appliances connected between L2 and G.
- Here is a basic diagram of the power feed to your house, according to what the power company said they found:
- 
- R1 represents the additional series resistance due to the cable being corroded. R2 represents the leakage current to ground due to the broken insulation. Both these can vary over time, whether it recently rained, and even recent usage. Significant usage will heat up R1, and various chemical effects can make R2 not even look like a resistor.
- However, this is still the basic concept. This alone explains nicely why the L2-G voltage is low, but not why L2-L1 could be lower than L2-G. For that we have to consider what is connected in the house.
- Here is the circuit considering some of what is in the house:
- 
- R3 shows the small but inevitable leakage and "phantom loads", and C1 capacitance between the wires and inside 240 V appliances.
- Note that both R3 and C1 can allow substantially more current than might be apparent at first glance. Modern appliances often use a little standby power, even when "off". There may be a clock, for example. Most modern appliances aren't turned on by actually switching main power directly by a button you touch. That would require way too large and expensive user buttons. Something has to always be on to sense when you press one of those little membrane panel buttons, for example.
- C1 isn't just the stray capacitance between wires in the walls. The large appliances in particular probably have hefty line filters to reduce their conducted emissions to just below the legal limit. There could easily be some deliberate capacitance across the power input for that purpose alone.
- The symptoms you found can be explained by the right relative values of the various components in the above circuit. To prove this, consider the extreme case where R1 and R2 are completely open:
- 
- With an infinite impedance voltmeter, you'd measure 120 V L1-G, 120 V L2-G, and 0 V L2-L1. Your actual case is somewhere between the top circuit and this last one. Hopefully you can see that with the various ratios between, R1, R2, R3, and C1, you can construct lots of different scenarios, including the one you actually had.
- <blockquote><ul>
- <li>The L1/G voltage difference was 120V (good).
- <li>The G/L2 voltage difference was 90V (bad).
- <li>The L1/L2 voltage difference was 30V (very bad!).
- </ul>
- </blockquote>
- Note that your numbers add up nicely if you assume the L2 connection from the street is completely open. In other words, all the L2 voltage you see is coming from L1. The 30 V L1-L2 is because phantom loads and leakage to ground on L2 pull down on what is getting dumped onto L2 from L1. That leakage is causing a 30 V drop, hence L2 is at 120 V - 30 V = 90 V. When you measure L2 to L1, you get that 30 V drop directly.
- In the context of the second schematic:<ul>
- <li>R1 = ∞
- <li>R2 = 3 * R3
- <li>C1 = 0
- </ul>
- This is all quite plausible, and doesn't require phase shifts to explain.
- <h2>Conclusion</h2>
- This simple scenario would exactly cause your measurements:
- 
- R2 is shown outside the house because it was originally drawn to model the leakage of the exposed cable to the ground. However, R2 is really the combination of all loads to ground on L2. The most substantial part of R2 may actually be in the house, in the form of phantom loads of 120 V appliances connected between L2 and G.
#5: Post edited
by
Olin Lathrop
·
2020-08-04T13:28:40Z (over 3 years ago)
- Here is a basic diagram of the power feed to your house, according to what the power company said they found:
- 
- R1 represents the additional series resistance due to the cable being corroded. R2 represents the leakage current to ground due to the broken insulation. Both these can vary over time, whether it recently rained, and even recent usage. Significant usage will heat up R1, and various chemical effects can make R2 not even look like a resistor.
- However, this is still the basic concept. This alone explains nicely why the L2-G voltage is low, but not why L2-L1 could be lower than L2-G. For that we have to consider what is connected in the house.
- Here is the circuit considering some of what is in the house:
- 
- R3 shows the small but inevitable leakage and "phantom loads", and C1 capacitance between the wires and inside 240 V appliances.
- Note that both R3 and C1 can allow substantially more current than might be apparent at first glance. Modern appliances often use a little standby power, even when "off". There may be a clock, for example. Most modern appliances aren't turned on by actually switching main power directly by a button you touch. That would require way too large and expensive user buttons. Something has to always be on to sense when you press one of those little membrane panel buttons, for example.
- C1 isn't just the stray capacitance between wires in the walls. The large appliances in particular probably have hefty line filters to reduce their conducted emissions to just below the legal limit. There could easily be some deliberate capacitance across the power input for that purpose alone.
- The symptoms you found can be explained by the right relative values of the various components in the above circuit. To prove this, consider the extreme case where R1 and R2 are completely open:
- 
- With an infinite impedance voltmeter, you'd measure 120 V L1-G, 120 V L2-G, and 0 V L2-L1. Your actual case is somewhere between the top circuit and this last one. Hopefully you can see that with the various ratios between, R1, R2, R3, and C1, you can construct lots of different scenarios, including the one you actually had.
- <blockquote><ul>
- <li>The L1/G voltage difference was 120V (good).
- <li>The G/L2 voltage difference was 90V (bad).
- <li>The L1/L2 voltage difference was 30V (very bad!).
- </ul>
- </blockquote>
- Note that your numbers add up nicely if you assume the L2 connection from the street is completely open. In other words, all the L2 voltage you see is coming from L1. The 30 V L1-L2 is because phantom loads and leakage to ground on L2 pull down on what is getting dumped onto L2 from L1. That leakage is causing a 30 V drop, hence L2 is at 120 V - 30 V = 90 V. When you measure L2 to L1, you get that 30 V drop directly.
- In the context of the second schematic:<ul>
- <li>R1 = ∞
- <li>R2 = 3 * R3
- <li>C1 = 0
- </ul>
This is all quite plausible, and doesn't require phase shifts to explain.
- Here is a basic diagram of the power feed to your house, according to what the power company said they found:
- 
- R1 represents the additional series resistance due to the cable being corroded. R2 represents the leakage current to ground due to the broken insulation. Both these can vary over time, whether it recently rained, and even recent usage. Significant usage will heat up R1, and various chemical effects can make R2 not even look like a resistor.
- However, this is still the basic concept. This alone explains nicely why the L2-G voltage is low, but not why L2-L1 could be lower than L2-G. For that we have to consider what is connected in the house.
- Here is the circuit considering some of what is in the house:
- 
- R3 shows the small but inevitable leakage and "phantom loads", and C1 capacitance between the wires and inside 240 V appliances.
- Note that both R3 and C1 can allow substantially more current than might be apparent at first glance. Modern appliances often use a little standby power, even when "off". There may be a clock, for example. Most modern appliances aren't turned on by actually switching main power directly by a button you touch. That would require way too large and expensive user buttons. Something has to always be on to sense when you press one of those little membrane panel buttons, for example.
- C1 isn't just the stray capacitance between wires in the walls. The large appliances in particular probably have hefty line filters to reduce their conducted emissions to just below the legal limit. There could easily be some deliberate capacitance across the power input for that purpose alone.
- The symptoms you found can be explained by the right relative values of the various components in the above circuit. To prove this, consider the extreme case where R1 and R2 are completely open:
- 
- With an infinite impedance voltmeter, you'd measure 120 V L1-G, 120 V L2-G, and 0 V L2-L1. Your actual case is somewhere between the top circuit and this last one. Hopefully you can see that with the various ratios between, R1, R2, R3, and C1, you can construct lots of different scenarios, including the one you actually had.
- <blockquote><ul>
- <li>The L1/G voltage difference was 120V (good).
- <li>The G/L2 voltage difference was 90V (bad).
- <li>The L1/L2 voltage difference was 30V (very bad!).
- </ul>
- </blockquote>
- Note that your numbers add up nicely if you assume the L2 connection from the street is completely open. In other words, all the L2 voltage you see is coming from L1. The 30 V L1-L2 is because phantom loads and leakage to ground on L2 pull down on what is getting dumped onto L2 from L1. That leakage is causing a 30 V drop, hence L2 is at 120 V - 30 V = 90 V. When you measure L2 to L1, you get that 30 V drop directly.
- In the context of the second schematic:<ul>
- <li>R1 = ∞
- <li>R2 = 3 * R3
- <li>C1 = 0
- </ul>
- This is all quite plausible, and doesn't require phase shifts to explain.
- <h2>Summary</h2>
- This simple scenario would exactly cause your measurements:
- 
- I show R2 outside the house because it was originally drawn to model the leakage of the exposed cable to the ground. However, R2 is really the combination of all loads to ground on L2. The most substantial part of R2 may actually be in the house, in the form of phantom loads of 120 V appliances connected between L2 and G.
#4: Post edited
by
Olin Lathrop
·
2020-08-03T20:09:57Z (over 3 years ago)
- Here is a basic diagram of the power feed to your house, according to what the power company said they found:
- 
- R1 represents the additional series resistance due to the cable being corroded. R2 represents the leakage current to ground due to the broken insulation. Both these can vary over time, whether it recently rained, and even recent usage. Significant usage will heat up R1, and various chemical effects can make R2 not even look like a resistor.
- However, this is still the basic concept. This alone explains nicely why the L2-G voltage is low, but not why L2-L1 could be lower than L2-G. For that we have to consider what is connected in the house.
- Here is the circuit considering some of what is in the house:
- 
- R3 shows the small but inevitable leakage and "phantom loads", and C1 capacitance between the wires and inside 240 V appliances.
Note that both R3 and C1 can allow substantially more current than might be apparent at first glance. Modern appliances often use a little standby power, even when "off". There may be a clock, for example. Most modern appliances aren't turned on by actually switching main power. That would require way too large and expensive user buttons. Something has to always be on to sense when you press one of those little membrane panel buttons, for example.- C1 isn't just the stray capacitance between wires in the walls. The large appliances in particular probably have hefty line filters to reduce their conducted emissions to just below the legal limit. There could easily be some deliberate capacitance across the power input for that purpose alone.
- The symptoms you found can be explained by the right relative values of the various components in the above circuit. To prove this, consider the extreme case where R1 and R2 are completely open:
- 
- With an infinite impedance voltmeter, you'd measure 120 V L1-G, 120 V L2-G, and 0 V L2-L1. Your actual case is somewhere between the top circuit and this last one. Hopefully you can see that with the various ratios between, R1, R2, R3, and C1, you can construct lots of different scenarios, including the one you actually had.
- <blockquote><ul>
- <li>The L1/G voltage difference was 120V (good).
- <li>The G/L2 voltage difference was 90V (bad).
- <li>The L1/L2 voltage difference was 30V (very bad!).
- </ul>
- </blockquote>
- Note that your numbers add up nicely if you assume the L2 connection from the street is completely open. In other words, all the L2 voltage you see is coming from L1. The 30 V L1-L2 is because phantom loads and leakage to ground on L2 pull down on what is getting dumped onto L2 from L1. That leakage is causing a 30 V drop, hence L2 is at 120 V - 30 V = 90 V. When you measure L2 to L1, you get that 30 V drop directly.
- In the context of the second schematic:<ul>
- <li>R1 = ∞
- <li>R2 = 3 * R3
- <li>C1 = 0
- </ul>
- This is all quite plausible, and doesn't require phase shifts to explain.
- Here is a basic diagram of the power feed to your house, according to what the power company said they found:
- 
- R1 represents the additional series resistance due to the cable being corroded. R2 represents the leakage current to ground due to the broken insulation. Both these can vary over time, whether it recently rained, and even recent usage. Significant usage will heat up R1, and various chemical effects can make R2 not even look like a resistor.
- However, this is still the basic concept. This alone explains nicely why the L2-G voltage is low, but not why L2-L1 could be lower than L2-G. For that we have to consider what is connected in the house.
- Here is the circuit considering some of what is in the house:
- 
- R3 shows the small but inevitable leakage and "phantom loads", and C1 capacitance between the wires and inside 240 V appliances.
- Note that both R3 and C1 can allow substantially more current than might be apparent at first glance. Modern appliances often use a little standby power, even when "off". There may be a clock, for example. Most modern appliances aren't turned on by actually switching main power directly by a button you touch. That would require way too large and expensive user buttons. Something has to always be on to sense when you press one of those little membrane panel buttons, for example.
- C1 isn't just the stray capacitance between wires in the walls. The large appliances in particular probably have hefty line filters to reduce their conducted emissions to just below the legal limit. There could easily be some deliberate capacitance across the power input for that purpose alone.
- The symptoms you found can be explained by the right relative values of the various components in the above circuit. To prove this, consider the extreme case where R1 and R2 are completely open:
- 
- With an infinite impedance voltmeter, you'd measure 120 V L1-G, 120 V L2-G, and 0 V L2-L1. Your actual case is somewhere between the top circuit and this last one. Hopefully you can see that with the various ratios between, R1, R2, R3, and C1, you can construct lots of different scenarios, including the one you actually had.
- <blockquote><ul>
- <li>The L1/G voltage difference was 120V (good).
- <li>The G/L2 voltage difference was 90V (bad).
- <li>The L1/L2 voltage difference was 30V (very bad!).
- </ul>
- </blockquote>
- Note that your numbers add up nicely if you assume the L2 connection from the street is completely open. In other words, all the L2 voltage you see is coming from L1. The 30 V L1-L2 is because phantom loads and leakage to ground on L2 pull down on what is getting dumped onto L2 from L1. That leakage is causing a 30 V drop, hence L2 is at 120 V - 30 V = 90 V. When you measure L2 to L1, you get that 30 V drop directly.
- In the context of the second schematic:<ul>
- <li>R1 = ∞
- <li>R2 = 3 * R3
- <li>C1 = 0
- </ul>
- This is all quite plausible, and doesn't require phase shifts to explain.
#3: Post edited
by
Olin Lathrop
·
2020-08-03T20:04:36Z (over 3 years ago)
- Here is a basic diagram of the power feed to your house, according to what the power company said they found:
- 
- R1 represents the additional series resistance due to the cable being corroded. R2 represents the leakage current to ground due to the broken insulation. Both these can vary over time, whether it recently rained, and even recent usage. Significant usage will heat up R1, and various chemical effects can make R2 not even look like a resistor.
- However, this is still the basic concept. This alone explains nicely why the L2-G voltage is low, but not why L2-L1 could be lower than L2-G. For that we have to consider what is connected in the house.
- Here is the circuit considering some of what is in the house:
- 
- R3 shows the small but inevitable leakage and "phantom loads", and C1 capacitance between the wires and inside 240 V appliances.
- Note that both R3 and C1 can allow substantially more current than might be apparent at first glance. Modern appliances often use a little standby power, even when "off". There may be a clock, for example. Most modern appliances aren't turned on by actually switching main power. That would require way too large and expensive user buttons. Something has to always be on to sense when you press one of those little membrane panel buttons, for example.
- C1 isn't just the stray capacitance between wires in the walls. The large appliances in particular probably have hefty line filters to reduce their conducted emissions to just below the legal limit. There could easily be some deliberate capacitance across the power input for that purpose alone.
- The symptoms you found can be explained by the right relative values of the various components in the above circuit. To prove this, consider the extreme case where R1 and R2 are completely open:
- 
With an infinite impedance voltmeter, you'd measure 120 V L1-G, 120 V L2-G, and 0 V L2-L1. Your actual case is somewhere between the top circuit and this last one. Hopefully you can see that with the various ratios between, R1, R2, R3, and C1, you can construct lots of different scenarios, including the one you actually had.
- Here is a basic diagram of the power feed to your house, according to what the power company said they found:
- 
- R1 represents the additional series resistance due to the cable being corroded. R2 represents the leakage current to ground due to the broken insulation. Both these can vary over time, whether it recently rained, and even recent usage. Significant usage will heat up R1, and various chemical effects can make R2 not even look like a resistor.
- However, this is still the basic concept. This alone explains nicely why the L2-G voltage is low, but not why L2-L1 could be lower than L2-G. For that we have to consider what is connected in the house.
- Here is the circuit considering some of what is in the house:
- 
- R3 shows the small but inevitable leakage and "phantom loads", and C1 capacitance between the wires and inside 240 V appliances.
- Note that both R3 and C1 can allow substantially more current than might be apparent at first glance. Modern appliances often use a little standby power, even when "off". There may be a clock, for example. Most modern appliances aren't turned on by actually switching main power. That would require way too large and expensive user buttons. Something has to always be on to sense when you press one of those little membrane panel buttons, for example.
- C1 isn't just the stray capacitance between wires in the walls. The large appliances in particular probably have hefty line filters to reduce their conducted emissions to just below the legal limit. There could easily be some deliberate capacitance across the power input for that purpose alone.
- The symptoms you found can be explained by the right relative values of the various components in the above circuit. To prove this, consider the extreme case where R1 and R2 are completely open:
- 
- With an infinite impedance voltmeter, you'd measure 120 V L1-G, 120 V L2-G, and 0 V L2-L1. Your actual case is somewhere between the top circuit and this last one. Hopefully you can see that with the various ratios between, R1, R2, R3, and C1, you can construct lots of different scenarios, including the one you actually had.
- <blockquote><ul>
- <li>The L1/G voltage difference was 120V (good).
- <li>The G/L2 voltage difference was 90V (bad).
- <li>The L1/L2 voltage difference was 30V (very bad!).
- </ul>
- </blockquote>
- Note that your numbers add up nicely if you assume the L2 connection from the street is completely open. In other words, all the L2 voltage you see is coming from L1. The 30 V L1-L2 is because phantom loads and leakage to ground on L2 pull down on what is getting dumped onto L2 from L1. That leakage is causing a 30 V drop, hence L2 is at 120 V - 30 V = 90 V. When you measure L2 to L1, you get that 30 V drop directly.
- In the context of the second schematic:<ul>
- <li>R1 = ∞
- <li>R2 = 3 * R3
- <li>C1 = 0
- </ul>
- This is all quite plausible, and doesn't require phase shifts to explain.
#2: Post edited
by
Olin Lathrop
·
2020-08-03T13:22:56Z (over 3 years ago)
- Here is a basic diagram of the power feed to your house, according to what the power company said they found:
- 
- R1 represents the additional series resistance due to the cable being corroded. R2 represents the leakage current to ground due to the broken insulation. Both these can vary over time, whether it recently rained, and even recent usage. Significant usage will heat up R1, and various chemical effects can make R2 not even look like a resistor.
- However, this is still the basic concept. This alone explains nicely why the L2-G voltage is low, but not why L2-L1 could be lower than L2-G. For that we have to consider what is connected in the house.
- Here is the circuit considering some of what is in the house:
- 
- R3 shows the small but inevitable leakage and "phantom loads", and C1 capacitance between the wires and inside 240 V appliances.
- Note that both R3 and C1 can allow substantially more current than might be apparent at first glance. Modern appliances often use a little standby power, even when "off". There may be a clock, for example. Most modern appliances aren't turned on by actually switching main power. That would require way too large and expensive user buttons. Something has to always be on to sense when you press one of those little membrane panel buttons, for example.
- C1 isn't just the stray capacitance between wires in the walls. The large appliances in particular probably have hefty line filters to reduce their conducted emissions to just below the legal limit. There could easily be some deliberate capacitance across the power input for that purpose alone.
- The symptoms you found can be explained by the right relative values of the various components in the above circuit. To prove this, consider the extreme case where R1 and R2 are completely open:
- 
With a infinite impedance voltmeter, you'd measure 120 V L1-G, 120V L2-G, and 0 V L2-L1. Your actual case is somewhere between the top circuit and this last one. Hopefully you can see that with the various ratios between, R1, R2, R3, and C1, you can construct lots of different scenarios, including the one you actually had.
- Here is a basic diagram of the power feed to your house, according to what the power company said they found:
- 
- R1 represents the additional series resistance due to the cable being corroded. R2 represents the leakage current to ground due to the broken insulation. Both these can vary over time, whether it recently rained, and even recent usage. Significant usage will heat up R1, and various chemical effects can make R2 not even look like a resistor.
- However, this is still the basic concept. This alone explains nicely why the L2-G voltage is low, but not why L2-L1 could be lower than L2-G. For that we have to consider what is connected in the house.
- Here is the circuit considering some of what is in the house:
- 
- R3 shows the small but inevitable leakage and "phantom loads", and C1 capacitance between the wires and inside 240 V appliances.
- Note that both R3 and C1 can allow substantially more current than might be apparent at first glance. Modern appliances often use a little standby power, even when "off". There may be a clock, for example. Most modern appliances aren't turned on by actually switching main power. That would require way too large and expensive user buttons. Something has to always be on to sense when you press one of those little membrane panel buttons, for example.
- C1 isn't just the stray capacitance between wires in the walls. The large appliances in particular probably have hefty line filters to reduce their conducted emissions to just below the legal limit. There could easily be some deliberate capacitance across the power input for that purpose alone.
- The symptoms you found can be explained by the right relative values of the various components in the above circuit. To prove this, consider the extreme case where R1 and R2 are completely open:
- 
- With an infinite impedance voltmeter, you'd measure 120 V L1-G, 120 V L2-G, and 0 V L2-L1. Your actual case is somewhere between the top circuit and this last one. Hopefully you can see that with the various ratios between, R1, R2, R3, and C1, you can construct lots of different scenarios, including the one you actually had.
#1: Initial revision
by
Olin Lathrop
·
2020-08-03T13:20:02Z (over 3 years ago)
Here is a basic diagram of the power feed to your house, according to what the power company said they found:  R1 represents the additional series resistance due to the cable being corroded. R2 represents the leakage current to ground due to the broken insulation. Both these can vary over time, whether it recently rained, and even recent usage. Significant usage will heat up R1, and various chemical effects can make R2 not even look like a resistor. However, this is still the basic concept. This alone explains nicely why the L2-G voltage is low, but not why L2-L1 could be lower than L2-G. For that we have to consider what is connected in the house. Here is the circuit considering some of what is in the house:  R3 shows the small but inevitable leakage and "phantom loads", and C1 capacitance between the wires and inside 240 V appliances. Note that both R3 and C1 can allow substantially more current than might be apparent at first glance. Modern appliances often use a little standby power, even when "off". There may be a clock, for example. Most modern appliances aren't turned on by actually switching main power. That would require way too large and expensive user buttons. Something has to always be on to sense when you press one of those little membrane panel buttons, for example. C1 isn't just the stray capacitance between wires in the walls. The large appliances in particular probably have hefty line filters to reduce their conducted emissions to just below the legal limit. There could easily be some deliberate capacitance across the power input for that purpose alone. The symptoms you found can be explained by the right relative values of the various components in the above circuit. To prove this, consider the extreme case where R1 and R2 are completely open:  With a infinite impedance voltmeter, you'd measure 120 V L1-G, 120V L2-G, and 0 V L2-L1. Your actual case is somewhere between the top circuit and this last one. Hopefully you can see that with the various ratios between, R1, R2, R3, and C1, you can construct lots of different scenarios, including the one you actually had.